Design and Fabrication of a Fiber based Waveguide Interferometer

• Main Authors: Chung-Kai Hsu, 徐仲凱
• Other Authors: Chau-Shioung Yeh
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/08787507658821661445

碩士 === 臺灣大學 === 應用力學研究所 === 96 === The fundamental theory of Waveguide Interferometry is the characteristics of total reflection and sensing by the evanescent wave. When coupling a light beam into a waveguide structure, we can get the information of the specimen from the interference signal produced by the reference and sample beams. The evanescent field is sensitive to the surface of guiding layer and different environment will induce different phase change of the light beam, so we can apply this property to detect the surface condition of dielectric media. In this dissertation, a fiber-based waveguide interferometer system that includes low-cost optical fiber based guiding tunnel was built. The principal goal is trying to design a fiber based chip that can be combined with the traditional Mach-Zehnder system. In order to simplify complicated steps before, I design a Teflon fixture that can fix fiber to make etching easier. Besides, there is a flow tunnel design to prevent that specimen pull apart the sensing fiber. This chip has many characteristics including simple structure、easy to fabricate and low-cost. In order to promote the yield of chip making, completely analysis so as to foster the fabrication process was made in this thesis. Because fiber coupler can couple the light beam completely, interference signal will be a single spot of light and need one photo detector to capture signal only. This method not only reduces the cost of system components but also realizes the goal to minimum system volume. The property of flexible of fiber make the volume of system smaller than before and system gets simpler, faster, and has higher sensitivity, so it has the potential to extend the current system into a handheld meter in the future. This fiber-based waveguide interferometry system has been proved to have ability of differentiating between different sample by using air and alcohol solution as the specimen. By way of experimental verifications, we can find that proper signal level change was found with respect to different alcohol and glucose concentrations solutions. In summary, this system was verified experimentally to be able to detect the refractive index changes on the waveguide surface.